Miscible chemical ordering in Ti-Cr-Mo quinary system by solid solution of Mo<sub>2</sub>Ti<sub>2</sub>AlC<sub>3</sub> and Cr<sub>2.5</sub>Ti<sub>1.5</sub>AlC<sub>3</sub> o-MAXs.

Du, Cheng-Feng; Wang, Chuanchao; Xu, Mengfei; Xue, Yaqing; Xue, Lili; Meng, Conghui; Wang, Long; Qi, Weihong et al. · Nat Commun · 2025

basic_science · Level V

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Abstract

Out-of-plane ordering is promising for separately adjusting the heterodesmic chemical bonding inside the MAX phase thus tuning their properties, while constructing the out-of-plane ordered-MAX (o-MAX) is still a challenge. In this work, a strategy towards o-MAX by solid solutions of two existing o-MAXs is verified, i.e., Cr<sub>2.5</sub>Ti<sub>1.5</sub>AlC<sub>3</sub> and Mo<sub>2</sub>Ti<sub>2</sub>AlC<sub>3</sub>, with controllable stoichiometric ratios (1:2, 1:1, and 2:1). A miscible chemical ordering is observed in three Ti-Cr-Mo quinary MAXs, which inherits the out-of-plane ordering from both parental o-MAXs. Meanwhile, through density functional theory (DFT) calculations, the electronic structure and bonding states inside the quinary o-MAXs are analyzed. Based on the calculations, anisotropic and improved mechanical properties are predicted, which agree with the experimental observed high compressive strength and tunable capacity of energy dissipation. The present work proves a promising way for synthesizing multicomponent o-MAXs.